C# 字符串引用未设置为字符串的实例。参数名称：输入ASP.Net MVC

为什么我看到这个错误prnt.sc/11btyns。只有当我将大多数时间从星期一改为最后一周的星期二，将周末改为最后一周的星期日时，才会发生这种情况

var mostRecentMonday = DateTime.Now.AddDays(-7).StartOfWeek(DayOfWeek.Monday); 
var weekEnd = mostRecentMonday.AddDays(7).AddSeconds(-1); 
var lastWeekMonday = mostRecentMonday.AddDays(-7).StartOfWeek(DayOfWeek.Monday); 
var lastWeekSunday = lastWeekMonday.AddDays(7).AddSeconds(-1); 

模范班

public DateTime? FeedbackDateTime { get; set; }

public DateTime? FeedbackSharedDateTime { get; set; }

public string AuditorAHT { get; set; }

ReportVM将数据分组并显示在视图中

public string FeedbackSharedBy { get; set; }
public int AuditCount { get; set; }

public string AudtAht { get; set; }

将审计员执行的操作保存为中的持续时间的控制器

public string AuditorAHT { get; set; }

下面的操作应显示审计员姓名、计数和平均花费时间

var audtName = db.Chats.Where(x => System.Data.Entity.DbFunctions.TruncateTime(x.MSTChatCreatedDateTime) >= mostRecentMonday
                           && System.Data.Entity.DbFunctions.TruncateTime(x.MSTChatCreatedDateTime) <= weekEnd && x.Feedback != null && x.FeedbackSharedBy != null).Select(x => new {
x.FeedbackSharedBy,
x.AuditorAHT
}).ToList() // this hits the database
                            
// We need to do grouping in the code (rather than the db)
// because timespans are stored as strings
.GroupBy(e => e.FeedbackSharedBy)
.Select(g => new ReportVM
{
FeedbackSharedBy = g.Key,
AuditCount = g.Count(),
AudtAht = TimeSpan.FromSeconds(g.Sum(t => TimeSpan.Parse(t.AuditorAHT).TotalSeconds / g.Count())).ToString()
})
.OrderByDescending(s => s.AuditCount).ToList();

ViewBag.AudtReport = audtName;

---

请建议

只需进行两次更改即可解决此问题

以下属性公共字符串AuditorAHT{get；set；}=“00:00:00”；。已更新，因此默认空值存储为00:00:00，而不是说空值

所有过去的数据都必须更新为00:00:00，因此运行SQL查询

构建项目，代码开始响应

---

谢谢大家!

StartOfWeek（）

从哪里来？日期时间EXNTE，上面的代码用Extn更新。请查看该代码中的任何地方都没有字符串，您需要向我们显示具有字符串的代码（或字符串解析）。@PeterB在我的问题中查看更新的代码。为什么要使用AddSeconds（），请删除它并进行测试。

var audtName = db.Chats.Where(x => System.Data.Entity.DbFunctions.TruncateTime(x.MSTChatCreatedDateTime) >= mostRecentMonday
                           && System.Data.Entity.DbFunctions.TruncateTime(x.MSTChatCreatedDateTime) <= weekEnd && x.Feedback != null && x.FeedbackSharedBy != null).Select(x => new {
x.FeedbackSharedBy,
x.AuditorAHT
}).ToList() // this hits the database
                            
// We need to do grouping in the code (rather than the db)
// because timespans are stored as strings
.GroupBy(e => e.FeedbackSharedBy)
.Select(g => new ReportVM
{
FeedbackSharedBy = g.Key,
AuditCount = g.Count(),
AudtAht = TimeSpan.FromSeconds(g.Sum(t => TimeSpan.Parse(t.AuditorAHT).TotalSeconds / g.Count())).ToString()
})
.OrderByDescending(s => s.AuditCount).ToList();

ViewBag.AudtReport = audtName;

public static class DateTimeExtensions
    {

        public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
        {
            int diff = (7 + (dt.DayOfWeek - startOfWeek)) % 7;
            return dt.AddDays(-1 * diff).Date;
        }

        static GregorianCalendar _gc = new GregorianCalendar();
        public static int GetWeekOfMonth(this DateTime time)
        {
            DateTime first = new DateTime(time.Year, time.Month, 1);
            return time.GetWeekOfYear() - first.GetWeekOfYear() + 1;
        }

        static int GetWeekOfYear(this DateTime time)
        {
            return _gc.GetWeekOfYear(time, CalendarWeekRule.FirstDay, DayOfWeek.Sunday);
        }
        static DateTime ToCleanDateTime(this DateTime dt)
        {
            return new DateTime(dt.Year, dt.Month, dt.Day, 0, 0, 0, 0);
        }

        public static DateTime ToCleanDateTime(this DateTime? dt)
        {
            if (dt.HasValue)
            {
                return dt.Value.ToCleanDateTime();
            }
            return DateTime.Now; // if dt doesn't have value, return current DateTime.
        }


    }

Update Chats
Set AuditorAHT = '00:00:00'
Where AuditorAHT IS NULL;